Measuring a flow of air or of other fluids through an opening is necessary or desirable in various contexts, for various reasons. For example, in an underground mine, adequate ventilation is necessary for the health and safety of the workers, and this requires a sufficient flow of air.
In the prior art, the air flow may be determined or estimated in various ways, one of which involves positioning transducers on opposite sides of an opening, aligned with each other for transmittal and receipt of signals from each other.
However, the transducers may become misaligned, after installation. For example, one or both of the transducers may be bumped by a passing vehicle, or by a worker passing by. Depending on the extent of the misalignment, however, the transducers may continue to be operational, and if the transducers remain operational, the misalignment may be undetected. Such misalignment can adversely affect the accuracy of the airflow determinations that are calculated based on the data from the misaligned transducers.
In particular, a relatively small misalignment can result in data that is inaccurate, but not obviously inaccurate. Because the data is inaccurate, the relatively small misalignment can cause errors in the airflow calculations that are not obviously errors. When the inaccuracies are relatively small, the misalignments may not be detected for some time. Even relatively small inaccuracies in the data can result in significant errors in measurements, especially if they continue over a relatively long time period.